Comprehensive Transcriptome Reveals an Opposite Regulatory Effect of Plant Growth Retardants in Controlling Seedling Overgrowth between Roots and Shoots

• Main Authors: Yanhai Ji, Guanxing Chen, Xuyang Zheng, Qiwen Zhong, Mingyun Zhang, Zhanhui Wu, Changlong Wen, Mingchi Liu
• Format: Article
• Language: English
• Published: MDPI AG 2019-07-01
• Series: International Journal of Molecular Sciences
• Subjects: plant growth retardants; gibberellins; overgrowth; transcriptome; tomato
• Online Access: https://www.mdpi.com/1422-0067/20/13/3307

Seedling overgrowth always develops in undernourished plants due to biotic or abiotic stresses, which significantly decrease the yield of crops and vegetables. It is known that the plant growth retardants paclobutrazol (PBZ) and chlormequat chloride (CCC) are the most commonly used chemicals in controlling seedling height in plants by regulating the gibberellin (GA) biosynthesis pathway. However, the exact molecular regulation mechanism remains largely unknown. This study performed a comprehensive transcriptome profile to identify significantly differentially expressed genes after adding CCC and PBZ to the water culture seedling raising system for the first time. According to the obviously restrained shoots and roots, the GA biosynthesis genes were significantly decreased, as well as the endogenous GA content being reduced. Intriguingly, the GA signaling pathway genes were affected in opposite ways, increasing in roots but decreasing in shoots, especially regarding the phytochrome interacting factor <i>SlPIF1</i> and the downstream genes expansins (<i>SlEXPs</i>), which promote cell wall remodeling. Further study found that the most down-regulated genes <i>SlEXPA5</i> and <i>SlEXPA15</i> were expressed specifically in shoot tissue, performing the function of repressing elongation, while the up-regulated genes <i>SlEXPB2</i> and <i>SlEXPB8</i> were proven to be root-specific expressed genes, which may promote horizontal elongation in roots. This research reported the comprehensive transcriptome profiling of plant growth retardants in controlling seedling overgrowth and restraining GA biosynthesis through the regulation of the GA signaling-related genes <i>SlPIF1</i> and <i>SlEXPs</i>, with an opposite expression pattern between roots and shoots.